VULCAN Solar Water Heater System

Page Content

About VULCAN

VULCAN is the brand name of TAQAMISR Evacuated Tubes or “Vacuum Tube” solar water heater. It uses the latest vacuum tube and heat pipe technologies to provide the most efficient solar water heater in Egypt.

What is Vacuum Tube?

Evacuated tubes absorb solar energy and convert it into heat for use in water heating. Each evacuated tube consists of two glass tubes made from extremely strong borosilicate glass. The outer tube is transparent and allows sunlight to pass through with minimal reflection. The inner tube is coated with a selective coating. This selective surface is excellent at absorbing solar radiation with minimal reflection losses.

The two tubes are fused together taking the air in-between out and creating vacuum that is the most important factor in achieving the high performance of the evacuated tubes.

Why vacuum?

Because it is an excellent insulator, which means there is no media to transfer heat out after it is absorbed by the inner tube.

The insulation properties are so good that while the inside of the tube may be 150oC, the outer tube remains within a few degrees of the ambient air temperature. This means that evacuated tube water heaters can perform well even in cold weather, while other types of collectors perform poorly in these conditions due to heat loss.

What is Heat Pipe?

Heat pipes might seem like a new concept, but you are probably using them every day and do not even know it. Laptop computers often using small heat pipes to conduct heat away from the CPU, and air-conditioning system commonly use heat pipes for heat conduction. In the VULCAN solar collectors, they are used to transfer heat from within the vacuum tube up to the header pipe that is housed in the insulated manifold box.

Structure & Operation

The pipe design comprises a long hollow copper pipe with a larger diameter bulb at one end. A small amount of high purity water is added into the heat pipe and then heated to high temperatures to evacuate any air from within the space. The result is a vacuum, similar to the space between the glass walls of the evacuated tube.

In a heat pipe, the vacuum is not used for insulation, but rather to alter the behavior of the liquid inside. At sea level water boils at 100oC, but if you climb to the top of a mountain, the boiling temperature will be lower. This is due to the difference in air pressure, and a vacuum is a state of very low pressure.Based on this principle of water boiling at a lower temperature with decreased air pressure, by evacuating the heat pipe we can achieve the same result.

The heat pipes used in VULCAN solar collectors have a boiling point of only around 30oC, so when the heat pipe is heated above this temperature the water begins to vaporize (turn to steam). This vapour rapidly rises to the top of the heat pipe and carries with it large amounts of heat. As the heat is off-loaded to the to the cooler liquid circulating through the solar collector header pipe at the bulb (top), the vapour condenses to form a liquid (water) and returns to the bottom of the heat pipe to once again repeat the cycle.